Seat suspension with cam support member and spring assisted height adjustment

ABSTRACT

A mechanical seat suspension inside a housing comprises parallel scissor arms and a support arm with a cam connected to suspension springs. The support arm, which carries the substantial majority of the seat load, has a height adjustment mechanism and a cam with two arcuate surfaces that define an imaginary pivot point. The use of the cam with the imaginary pivot point permits a more compact structure. Various embodiments of the support arm with a cam end and devices using the support arm are also disclosed. A shock absorber attached to the outside of the scissor arms dampens the stroke of the suspension springs connected to the cam. The ratio of the shock stroke travel to the vertical movement of the seat remains generally linear and constant, thus producing a more comfortable ride. Also included is a height adjustment mechanism on the support arm that interlocks with the cam by a pivoting pawl and biasing spring. The height of the seat is adjusted by the relative movement of the top portion of the housing to the lower portion. No external levers, triggers, or other structures are mecessary for seat adjustment. The tension in the suspension springs is adjustable to compensate for the weight of the rider. Another embodiment of the suspension includes a support assembly with two support arms that move relative to a cam that can be latched in five positions. Compression springs connected to the support assembly and disengaging arms with a disengaging roller permit a power assisted height adjustment.

BACKGROUND OF THE INVENTION

This is a continuation-in-part of our pending application Ser. No.305,464, filed Feb. 1, 1989, issued as U.S. Pat. No. 4,943,037 on Jul.24, 1990, which is a continuation-in-part of our pending applicationSer. No. 195,793, filed May 19, 1988, issued as U.S. Pat. No. 4,856,763on Aug. 15, 1989.

The present invention relates to various suspension mechanisms includingseat suspensions with height adjustment such as those typically used intrucks and construction and farming equipment.

There is a continuing need for suspension mechanisms that are simplyconstructed and inexpensive while still meeting manufacturers' everincreasing demands for compactness and comfort. An additional needexists for such a device whose suspension and ride characteristics canbe easily modified.

Some seat suspensions have damping means such as shock absorbers. Thesesuspensions have several problems. Most notably, the stroke of shockabsorbers does not have a linear relationship to the vertical movementof the seat. The nonlinear relationship between the stroke of the shockabsorber and the vertical movement of the seat diminishes theperformance and ride characteristics of such a suspension device.

In addition, shock absorbers or other such fluid devices often havedifficulty dissipating heat, especially when enclosed within a devicewhere air circulation is not adequate. This causes both poor performanceand a shorter life of the shock absorber.

Other difficulties have been encountered in the height adjustmentmechanisms of seat suspensions. Frequently such mechanisms are difficultto reach, require levers or triggers that can pinch an operator, andgenerally are complicated and expensive. Furthermore, such mechanismscan be dangerous to operate when a vehicle is moving and the operatormust grope or search for the adjustment mechanism.

Most seat suspensions are limited to a maximum of three heightadjustment positions, which limits the degree of comfort that can beobtained by a driver. Some seats are difficult to adjust verticallybecause of the inability elevate the seat upward. At the same time, inproviding a means with mechanical power to raise the seat, it isdesirable to continue to avoid having difficult to reach and difficultto operate levers to actuate the power height adjustment.

Finally, most seat suspensions transmit the load from the seat to thesuspension springs through steel bars comprising scissor arms orparallelogram linkages that carry virtually the entire load of the seat.These bars interact directly with the suspension springs. Thus, it hasbeen necessary for all of those bars to be of substantial construction,thus increasing the cost and complexity of such devices. Typical ofthese prior art devices include the following U.S. Pat. No. 3,339,906 toPersson; U.S. Pat. No. 3,826,457 to Huot de Longchamp; and U.S. Pat. No.4,125,242 to Meiller et al.

SUMMARY OF THE INVENTION

The present invention provides a less expensive, more compact andcomfortable seat suspension. It uses an independently operating supportarm with a cam that moves about an imaginary pivot. A damping means thathas a generally constant linear relationship to the vertical movement ofthe seat can also be incorporated.

One embodiment of the suspension device disclosed herein is enclosed ina suspension housing. The actual suspension function is provided by theprimary support means that is a support arm that pivots inside thehousing. In one preferred embodiment, a secondary support for thesuspension housing typically comprises parallel scissor arms which guidethe vertical movement of the housing and sustain a lesser amount of theforces generated by a load on the seat suspension. This occurs becausethe suspension means, such as extension springs, are directly connectedto the support arm and are not connected to the scissor arms. A heightadjustment means is part of the support arm. Attached to the secondarysupport--the scissor arms--is a damping means such as a shock absorber.

One of the objects of the present invention is to make a sturdy seatsuspension capable of fitting the stringent dimensional constraintsimposed by vehicle manufacturers. This is accomplished by theindependence of the support arm from the scissor arms and a design whichembodies an imaginary pivot defined by two arcuate surfaces on the camat the end of the support arm. Another feature of the present inventionis that it can be disassembled quickly and easily. Thus, the suspensionand ride characteristics of the present invention can be easily modifiedby changing different suspension springs and shock absorbers.

Another object accomplished by this seat suspension is its comfortableride. This is due to the physical independence of the suspension springsfrom the shock absorber. This feature of the present invention permits agenerally constant linear relationship between the vertical movement ofthe seat and the stroke travel of the damping means. That in turnresults in a more comfortable ride throughout the operational range ofmovement of the suspension.

In the preferred embodiment, the location of the shock absorber isoutside of the scissor arms, where it can be exposed to more freelycirculating air. Thus heat is dissipated from the shock absorber easily,permitting it to function more effectively and at the same timepreventing it from wearing out as quickly as prior art devices.

One embodiment of a height adjustment mechanism is incorporated into thesupport arm and requires no lever, trigger, or other means forvertically adjusting the seat suspension device. Such features can beincorporated but sometimes are deemed undesirable. Adjustment isaccomplished by pulling upwards on the top portion of the supporthousing, thus actuating a pivotable pawl and biasing spring that engagenotches on the cam that establish various vertical positions.

Another height adjustment mechanism includes an easily reached andactuated lever that provides a power height adjustment based upon theamount of weight, if any, acting on the suspension. A principal featureof this mechanism is at least one, and preferably two, support arms thatcan be spring biased relative to a cam to accomplish the heightadjustment. When the support arms and the cam are engaged, they form asupport arm assembly that, in combination with springs, maintains tosupport surfaces in spaced relation.

Because of its cost and structural advantages, the support arm itself isalso disclosed. The angularly displaceable support arm comprises a shaftwith two ends and is used in a suspension system that maintains twosurfaces in generally spaceable parallel relation. At one end of the armis a cam with two arcuate surfaces, one smaller and one larger. Thesesurfaces define a center point about which the cam pivots when thesupport arm is angularly displaced. At the other end of the shaft is ameans for permitting angular displacement of the shaft as the spacebetween the two surfaces connected to the suspension system changes,i.e., at least one surface moves relative to the other. The arm alsoincludes a means for operatively connecting the shaft to the suspensionmeans.

Alternative embodiments of a more simply constructed suspension systemthat use the support arm are also described. The strength andcompactness of the support arm permit the construction of a suspensionsystem without the scissor arms, the damping means, or the heightadjustment feature, although any one or more of these can be added. Thesuspension system comprises at least one moveable surface and includesthe support arm with the shaft and the cam with the two arcuate surfacesat one end. Cam follower means define the movement of the cam while abiasing means such as a spring or shock absorber controls the relativemovement of the two surfaces that are maintained in spaced relation bythe system. In suspension devices that use some form of cam device, withcam rollers or followers, it is desirable to minimize the number of camfollowers because of their cost. The present invention uses two heavyduty needle roller bearings as cam followers, while other devices usethree or more.

DESCRIPTION OF THE DRAWINGS

The novel features which are believed to be characteristic of theinvention are set forth in the appended claims. The invention itself,however, together with further objects and attendant advantages thereof,will be best understood by reference to the following description takenin connection with the accompanying drawings, in which:

FIG. 1 depicts a driver sitting on a seat attached to the top of themechanical seat suspension;

FIG. 2 is a perspective view of a mechanical seat suspension constructedin accordance with the present invention and with external parts brokenaway for better illustration;

FIG. 3 is an exploded view of the present invention;

FIG. 4 is a plan view of the mechanical seat suspension;

FIG. 5 is a side view in partial cross section along line 5--5 of FIG. 4and shows the invention at its highest adjusted position;

FIG. 6 is a side view in partial cross section, similar to FIG. 5,showing the mechanical seat suspension in its fully loaded or collapsedposition with the imaginary pivot located outside of the device;

FIG. 7 is a cross section along line 7--7 of FIG. 5 showing theindependent scissor arms and support arm inside the housing, with theshock absorber on the outside of one scissor arm;

FIG. 8 is an exploded view of the support arm showing in greater detailthe cam and the height adjustment means;

FIG. 9 depicts the height adjustment means in an unlatched position;

FIG. 10 depicts the height adjustment means latched in an intermediateposition;

FIG. 11 shows the height adjustment means reengaged in a first latchedposition;

FIG. 12 shows part of an unsatisfactory device in a raised position;

FIG. 13 shows the unsatisfactory device in an impossibly collapsedposition;

FIG. 14 is a perspective view of a support arm;

FIG. 15 is a sectional view in elevation of another embodiment of thesuspension system employing the support arm;

FIG. 16 is a sectional elevation view of the spring assisted heightadjustment mechanism in the low, unlatched position;

FIG. 17 is a cross sectional view of the spring assisted heightadjustment mechanism in the highest, unlatched position;

FIG. 18 is a cross sectional elevation view of the spring assistedheight adjustment mechanism in the latched position;

FIG. 19 is a perspective view of a seat suspension showing the parts ofthe spring assisted height adjustment mechanism;

FIG. 20 is a perspective view showing the relationship between a supportarm and cam with latch notches and latch pins;

FIG. 21 is a sectional view of the disengagement roller and roller platetaken through Section 21 of FIG. 17; and

FIG. 22 is a plan view of the seat suspension and height adjustmentmechanism viewed from the lower housing toward the upper housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 generally depicts the mechanical seat suspension device 1. Thedevice 1 is secured to a surface 2 in a vehicle (not shown) and can becovered by a seat 3 with pads or springs. The driver 4 sits upon theseat 3.

A general perspective of the present invention is shown in FIG. 2, whilean exploded view of the device 1 is depicted in FIG. 3. Preliminarilythe larger constituent parts of the device 1 will be discussed, afterwhich the individual pieces will be examined in detail, and then themethod of operation of the device 1 will be explained.

The housing for the device 1 consists of a lower portion 10 and upperportion 20. In this instance each portion is a solid plate withtransversely bent or welded edges; however, a substantial framelikestructure would also perform satisfactorily. Connected to the housingare parallel pairs of scissor arms 35, each pair being denoted 35A and35B respectively. One end of the scissor arms 35 is connected to theupper and lower housings 10, 20 by shaft bearing tubes 36 and 38 weldedto scissor arms 35. Threaded shafts 42 and 44 pass through holes 43 atthe ends of lower and upper housings 10, 20 and the bearing tubes 36,38. These shafts are secured at one end by nuts 46 (one shown) placedoutside the housing.

The other end of scissor arms 35 are welded to rods 37 and 39. Theserods 37, 39 are covered by nylon roller tips 40 that roll in channels 12and 22 of the lower and upper housings 10 and 20 respectively.

It can be seen from this configuration that the larger components of thedevice can be easily disassembled from a complete structure. By removingthe nuts 46 from the ends of the threaded shafts 42 and 44, and thenpulling the shafts 42, 44 free, the device will separate into the lowerand upper housings 10, 20 and the scissor arms 35.

Other preferred features of the invention include ears 13 for attachingthe upper housing 20 to a seat 3, and holes 14 for securing the lowerhousing 10 to a surface 2 in a vehicle. Also attached to the scissorarms 35 is the damping means, such as shock absorber 25. A dog 26 iswelded to one of the scissor arms. Rod 27, attached to dog 26, passesthough a journal 28 at one end of shock absorber 25 (FIG. 3). The otherjournal 28 of shock absorber 25 is pivotally engaged with rod 39 (FIG.7). The journal ends 28 can be frictionally isolated from the scissorarm 35 by nylon or rubber washers 29 (FIG. 2).

When only the scissor arms 35 and the housings 10, 20 are assembled,there is no force to keep the upper and lower housings 20, 10 spacedapart, and thus without the shock absorber 25, just these pieces wouldcollapse under their own weight. That is to say, there is no horizontalforce opposing roller tips 40 from sliding in channels 12, 22. In theassembled device 1, housings 10, 20 are connected to and spaced apart bya support arm assembly generally indicated as 60. One end of the supportarm 60 pivots in brackets 70 on the underside of upper housing 20 and isconnected to suspension means including springs 90. The other end of thesupport arm assembly 60 is welded to a transverse rod 62 with nylon endtips 64. These end tips 64 roll in channels 65 composed of steel plateswelded to lower housing 10.

The support arm assembly 60 is preferably comprised of two separatepieces 60A and 60B as shown in FIG. 8. The curved end of the support armassembly 60 fits between brackets 70. A spring shaft 92 passes throughbracket slots 72 and support arm slots 65. One set of ends of springs 90is operatively connected to spring shaft 92. The other ends of springs90 are ultimately secured against movement by indirect connection to theupper housing 20.

The general concept depicted thus far establishes the independentmechanical operation of the support arm 60 and the scissor arms 35. Thesupport arm assembly 60 ultimately engages the suspension means, springs90. The scissor arms independently interact with the damping means,shock absorber 25. When a load is placed on the device 1, the roundedends 61 of support arm assembly 60 roll or pivot against cam followers120 and 122 secured in bracket 70, thus pulling on suspension springs90. Simultaneously the motion of the springs 90 are damped by shockabsorber 25.

Thus the pivoting support arm 60 is the primary support means of thedevice The scissor arms 35 are a secondary support means that functionmostly as a guide means for the vertical motion of the upper housing 20.A structural analysis of the entire assembly when loaded would disclosethat the scissor arms 35 do transmit some vertical and horizontalcomponents of force, but those components are relatively small incomparison with the load sustained by the support arm assembly 60.Consequently, the scissor arms can be constructed of a less substantialand less costly amount of material than prior art devices.

The support arm assembly 60 is shown in exploded view in FIG. 8. Theassembly comprises the elements necessary to interact with thesuspension means and the elements making up the means to adjust theheight of the device 1. Cam 80 fits between pieces 60A and 60B. Springshaft 92 passes through slots 66, pieces 60A and 60B, and hole 81 in cam80 to secure one end of cam 80 inside the support arm 60. Pin 83 passesthrough slots 67 in pieces 60A and 60B and cam hole 82. Biasing spring85 is pinned (not shown) through the coil 87 of spring 85 between pieces60A and 60B with spring angle 86 fitting in notch 69. Pawl 95 is securedbetween 60A and 60B by pin 96 (FIG. 9) through holes 97A, 97B. On eachouter side of support arm 60, spring end rollers 100 with circular notch102 fit over each end of spring shaft 92 (FIG. 3). The rollers 100 aresecured to the two ends of the shaft 92 by locking pins 104 (one shown).Springs 90 have curved ends 90A that fit in notch 102 (FIG. 4 in planview). The ends of springs 90 connected to spring shaft 92 are moveable,as will be explained below. The fixed ends of springs 90 are curved ends90A that loop over bar 110 that is part of the suspension springadjustment mechanism.

As shown in FIG. 3, the spring adjustment mechanism consists of athreaded rod 112 threaded coupled to bar 110. The rod 112 extendsthrough an aligning hole (not shown) in the upper housing 20. One end ofthe rod 112 is secured to a knob 114 outside of upper housing while theother end is threadably secured by washer 117 and nut 118 to plate 116that abuts brackets 70. Consequently, when knob 114 turns threaded rod112, bar 110 moves toward knob 114 or toward brackets 70. This adjuststhe tension on springs 90. The force in the springs is ultimatelytransmitted to upper housing 20 by rod 112 and plate 116.

The functioning of the suspension system and its interaction withsupport arm 60 will now be described. One of the principal features ofthe device 1 is a so-called imaginary pivot that is the center of twoconcentric circles defined by arcuate surfaces 80A and 80B of cam 80(FIG. 9). These surfaces are always in contact with cylindrical camfollowers 120 and 122 that are secured inside brackets 70 (FIG. 3). Eachcam follower is rotatable about a fixed axis. Referring to FIGS. 5-7,when a vertical force A is applied to the upper housing 20, the entiresupport arm assembly moves in a predetermined manner. Rollers 64 slideto the right (FIG. 5) in slots 65 (FIG. 7) and the left side of thesupport arm 60 and the cam 80 pivot counterclockwise (FIG. 5). Thismovement occurs because cam followers 120 and 122 are fixed relative tothe position of brackets 70 and upper housing 20. Because springs 90 areconnected to spring shaft 92, and fixed relative to upper housing 20 bybar 110, springs 90 pull the cam 80 and the cam end of support arm 60 tothe right. The downward movement of the upper housing 20, however,causes a counterclockwise rotation to the cam 80 in opposition to forceA. As the cam 80 moves, so too does the imaginary pivot move verticallythrough space.

A comparison of FIGS. 5 and 6 demonstrates the circular movement of thecam 80 relative to the fixed locations of cam followers 120, 122. Fromthe highest adjustment of the device 1 as shown in FIG. 5, force A hascaused the cam 80 to rotate counterclockwise to the device's lowestposition in FIG. 6. At the same time, roller 64 of support arm 60 hasmoved further to the right, thus permitting the compression of thedevice 1. It should also be noted that slots 72 in brackets 70 definethe same concentric arc as do cam surfaces 80A and 80B moving againstcam followers 120, 122. Thus, spring shaft 92 follows the same arcuatemotion of the cam 80. It should be noted that FIGS. 5 and 6 representtwo different height adjustments of the device 1. As will become clearbelow, the height adjustment mechanism of the seat does not change whenthe device 1 is loaded. FIGS. 5 and 6 simply represent the two extremeconfigurations of the present invention.

FIG. 6 depicts the so-called imaginary pivot, which is defined by theintersecting radii of the arcs defined by cam surfaces 80A and 80B. Thepivot is not fixed, except with respect to the upper housing 20, and itslocation varies with the vertical movement of cam 80 and upper housing20. As can be seen from FIG. 6, the imaginary pivot can be locatedoutside the body of the device 1. This feature is responsible for thecompactness of the present invention. In the present embodiment, thecollapsed height in FIG. 6 is 3 inches, while the full height in FIG. 7is approximately 9 inches.

FIGS. 12 and 13 show how a traditional configuration would require agreater height for the same device. To duplicate the performance of thepresent invention would require a scissor arm 330 with a force lever armfrom pivot 300 to a point 310 collinear with spring 320. With thismechanical arrangement of FIG. 12, the completely collapsedconfiguration of FIG. 6 could not be achieved. This is demonstrated inFIG. 13, where the actual height H would be 5 inches, thus making itimpossible to bring together upper and lower housings 20, 10. The fewinches saved in the height of a mechanical seat suspension can mean thedifference between meeting and not meeting the dimensional tolerancesestablished by the equipment manufacturers who purchase such suspensiondevices. Traditionally the suspension of a device is determined by thelever ratio, which represents the vertical displacement of the upperhousing relative to the movement of the suspension spring. In the caseof the present invention, the radii of curvature of the cam surfaces 80Aand 80B are a result of the seat designer's predetermined choice of alever ratio, which in the present device is 3:1.

The independence of the support arm 60 from shock absorber 25 not onlypermits a more efficient operation of each item, it also permits agenerally constant linear relationship between the vertical travel ofthe upper housing 20 and shock absorber 25. This linearity results in auniformity of performance of the seat, regardless of its load or heightadjustment. The preferred ratio for the travel of the seat suspension tothe stroke travel of the damping means is approximately 3.

The linear relationship between the upper housing 20 and the shockabsorber 25 should not vary from complete linearity by more than 10percent. This is because the two ends of the shock absorber move in asubstantially linear relationship to each other as the scissor armsmove. In the prior art devices, the shock absorber would be attached tothe upper and lower housings. This would result in arcuate, non-linearmotion, and thus the vertical component of the force applied to theshock absorber would diminish as the vertical height of the suspensiondecreased. Here the force in the shock absorber 25 is independent(within 10 percent) of the height of the seat, and is determined only bythe load on the seat.

The height of the dog 26 determines the length of stroke of the shockabsorber 25. A maximum amount of stroke for the shock is desirable. Thefurther away from the scissor arms pivot 35C the rod 27 is, the greaterwill be the stroke of the shock absorber 25. This in turn will lower theratio between the displacement of the upper housing 20 and the shock 25.One of ordinary skill in the art will appreciate that it is notnecessary for the lever ratio and shock ratio to be identical, and thatsuch features are a result of the design requirements for a particularsuspension device.

FIGS. 9, 10, and 11 depict the operation of the height adjustment means.In general, biasing spring 85 urges pawl 95 into locked engagement withone of a plurality of notches 150 on cam 80. The notches 150 are definedby a plurality of teeth 152 and pawl engaging tooth 154. The describedembodiment of the present invention uses three notches, eachrepresenting a different height adjustment. Fewer or more notches can beused, and the disclosure of three height adjustments is merely by way ofexample.

FIG. 10 depicts the adjustment means at its intermediate height. Arrow Xdesignates the force of springs 90 which, coupled with the biasing forcefrom spring 85, maintains the tip of pawl 95 engaged with notch 150. Toraise the height of the device 1 requires the application of a verticalforce Y on spring shaft 92, which can be accomplished by an upward forceexerted on upper housing 20 (not shown). This causes support arm 60 topivot clockwise. Rollers 64 in channels 65 move to the left while thevertical force Y pulls the support arm 60 and cam 80 upward. Thisreleases the locking force engaging pawl 95 and notch 150 so that as cam80 is pulled upward pawl 95 slides over the tip of tooth 151 and intothe adjacent right hand notch 150A (FIG. 10).

In the described embodiment, notch 150A represents the highest heightadjustment. To lower the height of the device 1, additional verticalforce is applied to the support arm 60 and cam 80 until pawl disengagingedge 195 contacts cam disengaging edge 180. As more upward force isapplied pawl 95 pivots about pin 96. Thus the tip 295 of pawl 95 thatcontacts spring 85 moves from the tip 185 of spring 85 into notch 285.The tip of pawl 95 that engages notches 150 is moved beyond the arc thatcircumscribes teeth 151, and the height adjustment means is completelydisengaged.

Reengagement of the height adjustment means requires a downward force tobe applied to support arm 60 and cam 80. This is done by pushing down onthe upper housing 20 (not shown FIGS. 9-11), which rotates the supportarm 60 counterclockwise as rollers 64 move to the right. This motioneventually causes the tip of pawl 95 to contact pawl engaging tooth 154,which is larger than teeth 151. When contact is first made tip 295 isstill held in notch 285. Further downward force causes pawl 95 to pivotabout pin 96 so pawl tip 295 is relocated to spring tip 185. Thisarrangement is depicted in FIG. 11, which shows the height adjustmentmeans engaged in its first, or lowest, position.

It is important to note that the geometry of the biasing spring 85 andpawl 95 has a special configuration and purpose. When the heightadjustment means is in any of the three positions, or anywhere inbetween, rear pawl tip 295 is always located at biasing spring tip 185and being urged into engagement with notches 150. When the pawl 95 hasbecome completely disengaged, as shown in FIG. 9, notch 285 urgespivotable pawl 95 to remain in continual disengagement, outside the arcof teeth 151, until reengaging tooth 154 engages pawl 95 into the firstposition. The detent means of pawl disengaging edge 195 and camdisengaging edge 180, by causing the rotation of the pawl 95, locatesthe pawl tip 295 with respect to spring tip 185 or spring notch 285.

FIG. 14 is a perspective view of a simplified support arm 560 similar inconcept to the support assembly 60 described above. Because no heightadjustment mechanism is incorporated into the arm, it can be made as asingle structural element. The support arm 560 includes a shaft 562. Atone end of the shaft is cam 580, with a larger arcuate surface 561 and asmaller arcuate surface 566. The arcuate surfaces define a center pointC as depicted by the intersection of radii r₁ and r₂ in FIG. 15. At theopposite end of shaft 562 from cam 580 is a means 564 for permittingangular displacement of the support arm. Such means could consist merelyof a solid rod 564 as shown in FIG. 14, which would slide on a surface.Alternatively the means for permitting angular displacement could besimilar to the rollers 64 that slide in channels 65, as describedearlier. Various other equivalents of the means for permitting angulardisplacement can easily be substituted. For example, the end of shaft562 could merely be rounded for smooth sliding on a surface or could bea roller. The movement of the means 564 is generally parallel to the twosurfaces being supported.

A means for operatively connecting the support arm 560 to the remainderof the suspension system can be accomplished in a variety of ways. Rod592 can be secured to one end of a spring 600 as shown in FIG. 15. Otherfastening equivalents such as slots, nuts, bolts, weldments, and thelike are equally acceptable.

A practical but simplified version of a suspension system using thesupport arm 560 is depicted in FIG. 15. No height adjustment mechanism,scissor arms, or linear damping feature is present, although it iscontemplated that any one or more of those elements could be added.Instead of scissor arms, the stability of plate 520 is ensured by rod540 that travels in a pair of brackets with parallel slots 545 (oneshown), which in turn is secured to surface 547. Alternatively,stability of the support arm and the suspension system can be assured bya pair of plates 570, which function similarly to brackets 70 disclosedabove. Other means of stabilizing the suspension system are alsocontemplated, such as the above referenced rollers 64 and channels 65 orthe use of two parallel support arms (not shown).

Suspension spring 600 provides a biasing force to the system byresisting the rotation of support arm 560 as the cam follower means 522and 523 guide the movement of cam 580. In this way the support armfunctions essentially as described in the more complex system. Thespring 600, of course, can be fixed at one end 601 in various ways, suchas through tab 510 attached to plate 520. It is also contemplated thatthe biasing means could alternatively comprise other hydraulic ormechanical devices well known to those of skill in the art.

In FIG. 15 damping means 525 is a shock absorber shown in phantom whoselocation permits the depicted suspension system to collapse in much thesame way as shown in FIG. 6. Depending upon the desired motion and forcecharacteristics, as well as the dimensional and cost constraints, shockabsorber 525 could be eliminated; or, it could be relocated to avertical position between plate 520 and bottom surface 530 or otherdesirable positions.

As shown in FIG. 15, the simplified suspension system requires only onemoveable surface or plate 520. Surface 530 could be a parallel elementof the system, such as lower housing 10 described above, or it couldsimply be the flat floor of an operator's cab. Similarly, the suspensionsystems illustrated in the drawings can even be oriented 90 degrees to,for example, provide back support for a seat.

Another preferred embodiment of the present invention includes a supportassembly with a spring assisted height adjustment mechanism. The supportassembly itself, when latched in an adjusted position, operates aspreviously described (See, e.g., support arms 60A and 60B and cam 80 inFIG. 8, and FIG.'s 5 and 6 depicting the operation). The suspensionsystem includes a second support surface or lower housing 610 and afirst support surface or upper housing 620. Extensions support springs690 are connected at one end to the upper housing and at the other endto a spring shaft 692 that is operatively connected to the support armassembly 660 and support cam 680. The movement of the cam 680 isdetermined by curved surfaces on the cam that remain in contact with camfollowers 720 and 722. Two pairs of scissor arms 635 guide the motion ofthe suspension system and receive some of the force generated by weightapplied to the top of the upper housing. The bottom of the support armassembly has a roller assembly 664 that moves along the surface of thelower housing. Other similar features previously described also areincorporated in this embodiment, such as the spinner knob springadjustment 614 used to control the tension in extension spring 690 thatcontrols the suspension. A shock absorber 625, such as a three-wayadjustable Gabriel shock absorber, eliminates damping. The presentsuspension also contemplates certain improvements, such as bracketextension plates 670A (FIG. 22). These are used to distribute the forcefrom the suspension springs. In the embodiment depicted in FIG. 3, itwas discovered that stress concentrated in the area of brackets 70 wherethey connected to threaded rod 112. The extension plates 670A haveeliminated some of this stress concentration.

A clear view of the elements of the spring assisted height adjustmentmechanism is depicted in the perspective view of FIG. 19. Pulling up onheight adjustment handle 700 turns height adjustment rod 702, whichmoves a pair of disengagement drive arms 704 in the direction of arrowA. The disengagement arms have a slot 706 so that they can move freelywithout being obstructed by cam follower 722 which is secured tobrackets 670 in a manner described earlier. Cam follower 722 rotatesabout an axis but does not move relative to bracket 670, which is whyslots 706 are provided for the movement of disengagement arms 704. Atthe end of the disengagement arms is disengagement roller assembly 708,which is made up of three separate rollers, two of which contact thesupport arms 660 and the other of which engages roller plate 710 and isaligned with cam 680 (see FIG. 21). Spring shaft 692 is operativelyconnected to support extension springs 690, and also connected to theend of height adjustment spring guide 732. Spring guide 732 assures thelinear movement of height adjustment compression spring 730 which exertsa force as denoted by arrow C, FIG. 19. Between the pair of springs andspring guides is the support arm assembly which includes support arms660A and 660B and cam 680. These parts are also connected to springshaft 692. Shaft 692 passes through slot 666 in the support arms andthrough hole 682 in cam 680. Spring shaft 692 passes through a curvedslot (not shown) in brackets 670 similar to the slot 72 depicted in FIG.3. Support members 660A and 660B are connected by pins 695 that passthrough holes 697 and cam slot 751. Spring shaft 692 also maintains thesupport arms and cam 680 in the configurations depicted in FIGS. 16-19.Guide pin 783 passes through hole 667 and slot 681.

The spring assisted height adjustment mechanism operates as follows.When height adjustment handle 700 is actuated to move disengagementdrive arms in the direction of arrow A, the large center roller ofdisengagement roller assembly 708 encounters roller plate 710 whichtransfer the thrust of the disengagement arms through the outsiderollers of disengagement assembly 708 to push downward on the top ofsupport arms 660. As the top of the support arms move downward, pins 695move downward also, thus unlatching the pins from latching slots 750 andlatching teeth 752. While the support arms 660 move, cam 680 remainsstationary, because extension springs 690 are continually pulling springshaft 692 in the direction of arrow B (FIG. 16). The force in theextension support springs 690 is typically many times greater than theforce in height adjustment compression springs 730. When the cam rollersdisengage the support arms 660 from cam 680, height adjustmentcompression springs 730 exert a force as denoted by arrow C. Thevertical component of the force in the adjustment spring causes thespring guide to rotate in the direction of arrow R. The linear componentof the extension force is resisted by the much stronger supportextension springs 690. As the support arms 660, connected in part bypins 695, rotate and extend upward, support springs 690 urge the supportmembers and pins back into reengagement with latch slots 750. Thus, thesystem is randomly adjustable, based on whether the upper housing 620 isbearing any weight, and if so, how much. The use of two small pins 695permits a more even distribution of the force in spring 690, so thatteeth 752 and slots 750 in cam 680 can be machined to smallerdimensions, thus permitting a greater number of seat adjustmentpositions.

The spring assisted height adjustment mechanism possesses certainpreferred features. For example, the disengagement rollers 708 aredifferent sizes, as depicted in FIG. 21. If the rollers were the samesize, the two outside rollers would engage the support arms 660 wouldengage the support arms first. This would cause binding, scuffing, andwear of the two outside rollers. As depicted in FIG. 17, the uppersurface of cam 680 is recessed below the curved surface of support arm660 so that the smaller rollers will engage the support members beforethe larger roller engages the cam 680. Another preferred feature is forthe curved surfaces of cam 680 that engage cam followers 720 and 722 toextend slightly beyond the curved edges of support members 680. In thismanner, the cam followers wear better and therefore possess a longerlife if they contact only the hardened, smooth surface of the cam. Thecam is dimensioned more precisely than the support members. Therefore,if the support members were also contacting the cam followers, theimperfections in the curved surfaces of the support members would betransmitted through the suspension system to the driver, making for avery uncomfortable ride. Lock out plate 731 with tooth 731A (FIG. 22) isplaced so that the tooth will stop rotation of cam 680 and only supportarms 660 will move during the height adjustment operation.

Of course, it should be understood that various changes andmodifications to the preferred embodiments described herein will beapparent to those skilled in the art. Such changes and modifications canbe made without departing from the spirit and scope of the presentinvention and without diminishing its attendant advantages. It is,therefore, intended that such changes and modifications be covered bythe following claims.

What is claimed is:
 1. An angularly displaceable support assembly foruse in a suspension system that maintains two surfaces in generallyparallel spaced relation, comprising:at least one shaft with first andsecond ends; a cam movably connected to said first end to effect thespacing of the two parallel spaced surfaces, said cam having a largerarcuate surface and a smaller arcuate surface, said cam surfacesdefining a point about which said cam pivots as said shaft is angularlydisplaced; means for securing said shaft and said cam in fixedengagement; means for moving said shaft relative to said cam when saidcam and said shaft are disengaged; means disposed at said second end ofsaid shaft for permitting angular displacement of aid shaft as thedistance between the two parallel spaced surfaces changes; and means foroperatively connecting said shaft and said cam to the suspension system.2. The support assembly of claim 1 wherein said means for securing saidcam and said shaft further comprises a rod connectable to a biasingdevice in the suspension system.
 3. The support assembly of claim 1wherein said means for moving said shaft relative to said cam includes acompression spring.
 4. A suspension system for maintaining two surfacesin generally parallel relation, at least one of the surfaces beingmoveable with respect to the other, comprising:a shaft operativelyconnected to and angularly displaceable between the two surfaces; a cammovably connected to one end of said shaft, said cam having a largerarcuate surface and a smaller arcuate surface, said surfaces defining acenter point; means for disengaging said cam and said shaft; camfollower means for defining the movement of said cam and said shaft asthe one surface moves; biasing means operatively connected to said shaftfor controlling the relative movement of said shaft to said cam foradjusting the height of the one moveable surface; and means for biasingthe one moveable surface in relation to the other surface.
 5. Asuspension system, comprising:a first support surface and a secondsupport surface, generally parallel to each other; a pair of supportarms angularly disposed between and movably connected between said firstand second surfaces; a cam located at one end of and between saidsupport arms, said cam being in pivotal relation to and operativeconnection with said first surface, and said cam having a larger arcuatesurface and a smaller arcuate surface that define a center point aboutwhich said cam pivots; means for holding said cam and said support armsin fixed engagement; means for disengaging said support arms from saidcam; a first biasing means for moving said support arms relative to saidcam to adjust the height of said first surface; cam follower means inoperative contact with each of said arcuate surfaces for controlling themovement of said cam as one of said surfaces moves relative to the otherof said surfaces; means located at the other end of said support armsand in operative connection with said second surface for permitting achange in the angular disposition of said support arm while said firstand second surfaces move relative to each other; and a second biasingmeans in operative engagement with said support arms, with said cam andwith said first biasing means for providing a suspension force in thesuspension system.
 6. The apparatus of claim 5 wherein said firstbiasing means is a compression spring.
 7. The apparatus of claim 5wherein said second biasing means is an extension spring.
 8. Theapparatus of claim 5 wherein said cam includes latch means engageablewith pins connecting said support arms.